Littoral Maeridae and Melitidae (Amphipoda: Gammaridea) from the Gulf of Tehuantepec, Mexico Author García-Madrigal, María Del Socorro text Zootaxa 2010 2623 1 51 journal article 10.5281/zenodo.198142 0d39ac25-d25a-4d7d-b153-37cc3d70af80 1175-5326 198142 Elasmopus karlae n. sp. ( Figs 9 , 10 ) Type material: 4 specimens : UMAR-PERA-264, holotype male head lost (4.9 mm), paratype female ( 4 mm ) specimens mounted; paratypes 1 male , 1 female (La Tijera beach, April 30, 2005 , sediments from coral rock 4 m , coll. R. Bastida et al .). Description: based on holotype male, 4.9 mm, UMAR-PERA-264. Pereon: body dorsally smooth, color off-white in alcohol. Head lost. Coxae 1, 4 of length subequal, coxa 2 widest and coxa 3 narrowest; margin coxae 1–7 with sparse simple setae of medium to long, formula for coxae 1–7: 7–4–3–1–0–3–5; ventral margin of coxae 5, 6 with robust setae, formula for coxae 5–6: 4–1; anterior margin of coxa 1 and posterior margin of coxa 4 slightly emarginated; coxa 2 with lateral margins slightly rounded; coxa 3 with anterior margin slightly rounded and posterior margin slightly emarginated; coxa 7 suboblong, with long and short simple setae. Gnathopod 1: subtrapezoid propodus; palm margin denticulate and with numerous short robust setae; two robust setae at inner angle of the palm, one a short robust seta and the other longer. Gnathopod 2 sexually dimorphic, propodus of gnathopod 2 subrectangle, propodus is the same length as the dactyl; palm with short scarce simple setae, palm margin with two spines and two humps: first is a large rounded hump near dactylar hinge with four short robust setae on inner face; the second is an acute spine proximal to large setose hump and angled forward towards first hump, with two short robust setae on inner face and one longer on outer face; third is a long medial sharp middle spine, and fourth hump is large and rounded to receive dactyl; the fourth hump is out of the general line of palm margin of gnathopod 2; along the palm margin between proximal hump and medial spine there are four short robust setae and simple setae. Basis of pereopods 1–2 with long simple setae; pereopod 2 shorter than the pereopod 1; posterior margin of pereopods 3–5 minutely serrated and with short simple setae; basis of pereopods 3 and 5 nearly semicircular and wider than pereopod 4; pereopods 4 and 5 almost equal in length, but pereopod 5 stouter than pereopod 4. Pleon: epimera continuous with respect to general line of the body; ventral margin bearing only some short robust setae, formula for epimera 1–3 is 1:2, 2:1–2–2–1, 3:1–1–2, posterior edge of epimeron 3 lightly convex and bearing slight acclivities with short simple setae, emarginated posteroventral corner bearing a short denticle. Uropod 3 long, inner ramous 1/5 shorter than outer ramous; outer margin of outer ramous and inner margin of inner ramous each have three clusters of medial short robust setae; distal margin of peduncle with three pairs of short robust setae, one medial pair and one pair on each side. Telson deeply cleft, lobes excavated, apices armed with 3–5 robust setae, two long and 2–3 short, intercalated; longest robust seta is approximately 6/7 longer than the shortest robust seta; lateral margins of lobes with two plumose setae and one plumose setae on outer angle of each lobe. Female: based on paratype female, 4 mm , UMAR-PERA-264. Body: length is approximately 2/3 longer than the antenna 1; dorsally smooth; color off-white in alcohol. Head the same size as the combined length of the first two pereon segments; anterior head lobes broadly rounded, and inferior antennal rounded. Epimera: ventral margin bearing only some short robust setae, formula for epimera is 1:1, 2:1, 3:1–1–2–1. Eyes: long, round to oval, light brown pigment; width represents approximately 1/3 the length of head. Antenna 1: stout and short, length is approximately 1/3 the length of the body, first article of peduncle is approximately 1/8 shorter and 1/5 thicker than the second article, third article of peduncle 3/5 of the length of second article. Accessory flagellum with two articles, both the same length. Antenna 2 feeble, less than 1/2 the length of the antenna 1; article 4 is 1/5 longer than the article 5; first article of flagellum is 1/5 the length of the fifth article of peduncle. Gnathopod 1: subquadrangular propodus, oblique palm margin, minutely denticulated and with numerous small robust setae; longer robust seta at inner angle of the palm. Gnathopod 2: subtriangular propodus, propodus 1/2 longer than the dactyl; palm with scarce medium-sized setae, oblique palm margin with short robust setae and half of this margin minutely denticulated, a longest robust seta at inferior lateral of propodus; inner margin of dactyl denticulated. Uropod 3: external margin of outer ramous with two bundles of robust setae and a singular robust seta, inner margin of the inner ramous with two medial robust setae; distal margin of peduncle with short robust setae, a pair of distal robust setae on inner angle, one medial robust seta and one on the external angle. Telson: apices armed with 3–4 robust setae, two long and 1–2 short intercalated. FIGURE 9. Elasmopus karlae n. sp. , paratype, female, 4 mm, UMAR-PERA-264, from La Tijera, Oaxaca: A) habitus ; B) accessory flagellum. Holotype, male, 4.9 mm, UMAR-PERA-264, La Tijera, Oaxaca: C) coxa 1; D) coxa 2; E) coxa 3; F) coxa 4; G) coxa 5; H) coxa 6; I) coxa 7; J) gnathopod 2, internal side; K) gnathopod 2, external side; L) gnathopod 1, internal side; M) epimera; N) uropod 1; O) uropod 2; P) gnathopod 1, external side. FIGURE 10. Elasmopus karlae n. sp. , holotype, male, 4.9 mm, UMAR-PERA-264, La Tijera, Oaxaca: A) uropod 3; B) telson; C) pereopod 1; D) pereopod 2; E) pereopod 3; F) pereopod 4; G) pereopod 5. Paratype, female, 4 mm, UMAR- PERA-264, La Tijera, Oaxaca: H) upper lip; I) lower lip; J) uropod 3; K) telson; L) maxilliped; M) right mandible; N) maxilla 1; O) maxilla 2; P) gnathopod 1, external side; Q) gnathopod 1, internal side; R) gnathopod 2, external side; R) gnathopod 2, internal side. Etymology : the specific name is dedicated to my oldest daughter, for all of her time dedicated to the search, collection, and organization of literature on amphipods for my work. Taxonomic comments: Elasmopus karlae n. sp. does not resemble any other species of Elasmopus described in the world, mainly in morphology of gnathopod 2. Remarks : headless terminal male holotype was chosen because of the major characters such as gnathopod 2, coxae, pereopods, epimera, uropods and telson in excellent condition. In addition, there is another subterminal male that allowed the corroboration of similitude with the females. For this reason, the female head, antenna 1–2, eyes and mouthparts are described and illustrated.